1. Field of the Invention
The invention relates to a process for producing thermosetting resins of the rapid hardening type by using a novel catalyst.
2. Description of The Prior Art
It has been reported by Tsuzaki, Ichikawa and Kase that a cyclic carbonate reacts with an isocyanate compound in the presence of a tertiary amine to form a molecular complex with trimerization of the isocyanate groups (i.e., formation of an isocyanurate ring) and, when heated, to form an oxazolidone ring with evolution of carbon dioxide, and that a resin is formed when the isocyanate compound is a polyvalent compound [J. Org. Chem., 25, 1009 (1960)]. It has also been reported by Gaul and Nguyen that a mixture of a polyvalent isocyanate and a cyclic carbonate is heated to form a thermosetting resin useful as an adhesive (Belgian Pat. No. 891,879; U.S. Pat. No. 4,359,507; CA No. 100, 105, 388).
However, the prior art processes using a tertiary amine as the catalyst are disadvantageous in that the resulting polymer tends to assume a reddish brown color and produce a significant amount of gas bubbles. Moreover, when the reaction is carried out a large scale, the amine gives off an irritant odor. Thus, there is a large demand for nonvolatile catalysts.